On capacity and blocking of multi service CDMA systems with smart antennas

In this paper we investigate the uplink capacity of multi service CDMA systems which incorporate smart antennas at the base station (BS) site. Therefore we model the CDMA system as interference limited and apply an interference based call admission control (CAC). Smart antenna beamforming at the BS site is considered and modeled by brickwall (sometimes referred to as key hole) antenna patterns (the obtained results, however, include omnidirectional systems as a sub-case). Spatial teletraffic is modeled by a two dimensional Poisson point process. Users of n different service classes are then modeled by n independent random variables. Based on the CAC we discuss the system capacity and derive blocking probabilities for the cases of one service class and n service classes, respectively. Numerical results are provided for the case of n = 2 service classes, where admission and blocking probabilities are presented as functions of carried and offered traffic, respectively.